DNA REPLICATION

DNA replication is the process where DNA makes same copies of itself . Replication occurs at the rate of between 50 nucleotide per second ( in mammals ) and 500 nucleotides per second ( in bacteria). Watson and crick give this mechanism basis on their double helical structure Each strand of DNA serves as a template on which its complementary strand is synthesised . This method of DNA replication is described as semi - conservative , because each daughter DNA molecule is a hybrid conserving one parental polynucleotide strand and the other one newly synthesised strand.

Important Point of Replication Process-

1. The base pairing during DNA replication, i.e., adenine pairs with thymine and guanine with cytosine.
2. Nucleotide monomers are added one by one to the 3 ' end of the growing strand by the enzyme DNA polymerase. 
3. The sequence of nitrogenous bases in each daughter strand being formed is complementary to the base sequence in the template strand. 
4. C - 3 ' carbon of deoxyribose present on the 3 ' end of the new polynucleotide chain of DNA has OH group and is free to bind to another nucleotide . C - 5 ' carbon of deoxyribose on the 5 ' end of polynucleotide chain has a phosphate . Therefore , the new polynucleotide chain is always synthesized in 5 ' → 3 ' direction.

Requirements for DNA Replication

1. Precursor nucleotide molecules- dNTPs, dATPs, dGTPs, dCTPs, dTTPs.
2. Template DNA 
3. RNA Primer
4. Enzyme-DNA polymerase, Ligase, helicases.
5. Proteins-DNaA, SSB protein